The history of Jephthah appears to be an independent history inserted by the compiler of the Book of Judges. Judges 11:4-5 introduce the Ammonite war without any apparent reference to Judges 10:17-18.
A genealogy of Manasseh 1 Chronicles 7:14-17 gives the families which sprang from Gilead, and among them mention is made of an “Aramitess” concubine as the mother of one family. Jephthah, the son of Gilead by a strange woman, fled, after his father’s death, to the land of Tob Judges 11:3, presumably the land of his maternal ancestors (compare Judges 9:1) and an “Aramean” settlement (2 Samuel 10:6, 2 Samuel 10:8; 2 Samuel 1 Macc. 5:13). It is difficult to conceive that Jephthah was literally the son of Gilead, if Gilead was the son of Machir, the son of Manasseh. Possibly “Gilead” here denotes the heir of Gilead, the head of the family, whose individual name has not been preserved, nor the time when he lived.